Lysozyme (EC 3.2.1.17), also known as muramidase or N-acetylmuramide glycanhydrolase, catalyzes hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins.
Lysozyme is typically produced as a defensive mechanism against bacteria by many organisms as viruses, plants, insects, birds, reptiles and mammals. The enzyme causes the hydrolysis of bacterial cell walls by cleaving the glycosidic bonds of peptidoglycan; an important structural molecule in bacteria. After having their cell walls weakened by lysozyme action, bacterial cells lyse resulting from osmotic pressure. There is an increasing interest in the potential of lysozyme enzymes as antimicrobial agents. For example, lysozyme activity has been shown against pathogens such as Streptococcus pneumoniae, Bacillus anthracis, Enterococcus faecium, Bacillus stearothermophilus, Clostridium botulinum, Clostridium butyricum, Clostridium perfringens, Clostridium sporogenes, Clostridium tyrobutyricum, and Listeria monocytogenes. 
Lysozyme has been classified into five different glycoside hydrolase (GH) families (CAZy, www.cazy.org): hen egg-white lysozyme (GH22), goose egg-white lysozyme (GH23), bacteriophage T4 lysozyme (GH24), Sphingomonas flagellar protein (GH73) and Chalaropsis lysozymes (GH25). The lysozyme family GH25 has been found to be structurally unrelated to the other lysozyme families.
Use of lysozyme has been suggested in animal feed (see for example WO 00/21381 and WO 04/026334), in cheese production (see for example WO 05/080559), food preservation (Hughey and Johnson (1987) Appl Environ Microbiol 53:2165), detergents (see for example U.S. Pat. No. 5,041,236 and EP 0425016), in oral care (see for example U.S. Pat. No. 4,355,022, WO 04/017988 and WO 08/124,764), cosmetology and dermatology, contraception, urology, and gynaecology (see for example WO 08/124,764).
Hen egg-white lysozyme is a commercially available lysozyme product. Lysozymes isolated from microbial sources are also known.